To provide a battery enabling a traceability check by a nondestructive method.

A lithium ion secondary battery comprises an electrode body containing a positive electrode, a negative electrode, and a separator, and an electrolyte in an exterior body. The exterior body is made of a radiolucent material, an identification mark is provided on a radiolucent member of the electrode body, and the identification mark comprises at least an X-ray absorbing filler and a binder. The lithium ion secondary battery may further comprise an insulator at the top and/or the bottom of the electrode body, and the identification mark may be provided on the insulator.